This invention broadly relates to high pressure grease fittings and check valves used in conjunction with pumps, valves, flow actuators, compressors, or similar devices. More particularly the present invention relates to high pressure fittings and check valves in which internal flow control apparatus is employed to reduce or prevent blow-out, plugging or the like.
As will be recognized by those skilled in the art, a wide variety of grease fittings have previously been employed to facilitate the introduction of lubricants and the like into equipment having various moving internal parts. In oil and gas pipeline apparatus such as pumps, valves, flow actuators, and compressors, extremely high pressures may be commonly required to inject lubricants. The dynamic configuration of oil and gas equipment generates significant frictional forces, heat, thermal expansion and contraction, etc., which in time, severely stresses the seals, gaskets, and other internal components, ultimately denigrating the integrity and safety of the equipment. As a remedial maintenance measure viscous sealants, lubricants, grease, or the like, are periodically injected into such equipment. Servicing the equipment in this manner effectively prolongs equipment life and continuity of the system in which the equipment is a part. Those skilled in the art commonly recognize that the viscosity of the sealant, grease, lubricant, or the like, is directly proportional to its sealing and lubricating capability.
"Heavy duty" sealants and lubricants, are quite effective when sealing, high pressure equipment. Typical commercially available lubricating and/or sealing substances, that in addition to being highly viscous, teem with minute solid particles called "bridging agents." These bridging agents aid in sealing the gaps, cracks, leaks, holes, etc., within the equipment being serviced by collectively joining or spanning the opposing sides of the gap, or crack to effectuate sealing. In oil and gas pipeline applications the force feeding of "heavy" grease, sealants, lubricants, or the like, may necessitate input pressures in excess of 15,000 PSI. Typical high pressure grease fittings such as "button-head" fittings are widely used. A button-head fitting allows the grease or injection gun to be securely fastened to the inlet of the fitting during the introduction of the lubricant, or sealant.
However, prior art button head fittings, high pressure check valves, and the like have suffered from a variety of problems. Until now, there has been no button-head styled fitting commercially available which will perform consistently and flawlessly, delivering the injected heavy substance to the equipment being serviced. Hence, because of their design, injection of heavy sealants, or lubricants into the prior art grease fittings has proven quite problematic. Many known prior art fittings in this field of invention employ a "soft seat." This soft seat is formed by a ball, usually of steel construction, forcibly in contact with a non-metallic elastomer ring, washer, or cup. The purpose of the seat is to prevent reverse flow from escaping the fitting through the inlet end, and to prohibit unwanted matter from entering the fitting while not in use. A soft elastomer seat is advantageous because it can facilitate drip tight sealing. However, soft seats wear out quickly when subjected to sustained pressures.
As will be appreciated by those skilled in the art, soft seats can be disadvantageous when the fitting or valve is constantly subjected to high back pressures. At low pressures, a slight leak will cause the seat to "cut-out" (become grooved), often resulting in permanent leaks. At high pressures the whole seat can become distorted, thus limiting the usefulness of the fitting. Considering the nature of heavy sealants, or lubricants, such as they are, a metal-to-metal seal provides adequate sealing for a pressurized highly viscous substance. Because seals wear out so often, it is common to inject fittings with bridging agents, but this tactic results in other problems.
In addition to the unreliability of the seals associated with prior art fittings, the injection of heavy substances has created numerous other problems, such as fitting "plug-off" (clogging). A major cause of this relates to failure of the usual valve element return spring. Spring deformation often results when the check valve element, usually a sphere, depresses the spring into an over compressed state. In addition, spring twisting and bending can occur unless spring movements are rigorously constrained. A severe problem is "cylinderization," wherein the return spring is compressed until its adjacent windings abut one another, and the spring thus forms a cylinder-like or tube. Since the required grease flow path is through the spring interior and through adjacent windings, cylinderization cuts off fitting flow integrity. Hence, flow between successive spring coils is substantially restricted by cylinderization. Further complicating matters, the ball elements common in the vast majority of prior art fittings reposition themselves atop the compressed spring. Consequently, the axial passageway within the spring is also substantially closed off. Hence, the injection pressure may not be dissipated, and blow out of the fitting can occur. When the fitting blows, gas back pressure can result in a calamity. Also, when spring flow is jammed, as when heavy substances clog and obstruct the flow paths, improper lubrication of the serviced device may result. When the grease gun is uncoupled from the fitting, unwanted gas venting may occur. Even if the jammed fitting does provide a seal, when grease input pressure is thereafter relaxed, the accumulated bridging agents may prevent valve closure, resulting in a ruined fitting.
The teachings of the prior art do not suggest an adequate solution to spring cylinderization or fitting plug-off. We have found that all prior art fittings known to us will plug-off at some time, especially when repeatedly injected with the heaviest known sealants, lubricants, and bridging agents. Once a fitting plugs-off, its utility is substantially diminished, and attempts to clear the fitting by increasing the localized pressure within the fitting body will most often result in fitting "blow-out."
"Blowout" occurs when an induced pressure change in a plugged fitting causes the bottom crimp, or retaining ring to fail. Said failure is evidenced by a sudden drop in pressure as indicated by the grease gun pressure gage. When blow-out does occur, the internal parts of the fitting are jettisoned into the equipment being serviced. Now costly and time consuming "blowdown" (evacuation) of the attached pipeline or flow line must be initiated so as to facilitate replacement of the collapsed fitting, and repairs to any damaged equipment. Thus, an object of the present invention is to prevent those events that could possibly lead to fitting blow-out from happening.
It is thus highly desirable for one to develop a fitting which is designed to forbid spring deformations such as cylinderization, and which is immune to fitting plug-off.
The pertinent prior art in this field of invention does not successfully address these problems. United States Pat. No. 4,347,915 employs an offset "leg" of the spring member to cause the ball member to drift to one side when the spring compresses. Theoretically, this ball drift increases the size of the flow channel within the axial hollow portion of the spring, and insures that the flow continues even if the spring is completely cylinderized. However, when very heavy sealants with large bridging agents are injected into the fitting, the ball forces the leg member to bend downward during spring compression and ultimate cylinderization, permitting the ball member to substantially diminish the flow channel. Hence, this fitting has the propensity to plug-off. The latter reference also discloses an internal sleeve member not found in other sources of prior art. The addition of the sleeve is an attempt to prolong the soft seat life, and avoid the soft seat denigration as alluded to earlier. The sleeve does virtually nothing to prevent spring cylinderization and the associated fitting plug-off. U.S. Pat. No. 4,512,441 discloses a stinger assembly employed for ball-to-seat sealing purposes. The spring may still cylinderize within the stinger assembly making plug-off possible.
U.S. Pat. Nos. 2,918,084 and 3,437,082 disclose a variety of spring, ball, and sleeve configurations. There is no means in any these patents by which the spring members are prevented from cylinderizing. More importantly however, the flow paths or channels in each of the above listed patents can be severely diminished and restricted.
In summation, there is a definite need for a flow fitting to withstand high localized pressures, to accept very heavy sealants and lubricants in order to prolong equipment life, and to provide substantially unrestricted flow channels in which the injected sealants, lubricants, or the like, could travel without plugging-off the fitting.